An image capture apparatus is able to scan a document and convert the document image information thereon into representative digital electrical signals that are then transmitted to a user device, such as a computer, for processing. The ability of a user device to thus process document image data in the form of electrical signals makes it possible to store, retrieve, duplicate, and transmit large quantities of the document image data at high rates of speed. Such image capture apparatus provides for high-speed processing of the growing quantities of information generated by modern society.
Referring now to FIG. 1, there is shown a prior art image capture apparatus 30 that is able to simultaneously scan both sides of a document 60. The prior art image capture apparatus 30 comprises a document feeder section (FEEDER) 40 (shown within a dashed-line rectangle) that feeds documents 60 to be scanned one at a time into the image capture apparatus 30, a document transport section (DOC. TRANSPORT) 41 (shown within a dashed-line block) that transports the documents 60 from the document feeder section 40 in a first direction to a second direction orthogonal to the first direction, a read section (READ) 42 (shown within a dashed-line rectangle) where the documents 60 are received from the document transport section 41 and scanned, and a document exit section (EXIT) 43 (shown as a dashed-line rectangle without components) to which the documents 60 are sent that have been scanned in the read section 42.
In the document feeder section 40, the documents 60 are stacked in a feed tray 50 from where the documents 60 are fed preferably one at a time to the document transport section 41. Provided near the document feed tray 50 are a feed roller 51 and a mutually opposed retard roller 52. A topmost document 60 is drawn into the document transport section 41 by the counterclockwise rotation of a feed roller 51 (shown by the arrow within roller 51). At the same time, the counterclockwise rotation of a retard roller 52 (shown by the arrow within roller 52) serves to urge the documents 60 below the topmost document 60 on the stack of documents 60 back towards the document feed tray 50. The document transport section 41 comprises transport rollers 53, conveyor belt means 54, and pressure rollers 55 that convey each document 60 from the feeder section 40 to the read section 42. The read section 42 comprises two aperture plates 56 arranged in mutual opposition which are separated by a prescribed distance, two light sources 57, and two optical sensors 58. In the read section 42, a prescribed region (not shown) of each side of each document 60 passing between the aperture plates 56 is concurrently illuminated by a separate beam of light (not shown) from a separate light source 57 and concurrently scanned. Light reflected by each side of the document 60 is detected by a separate optical sensor 58, such as a charge-coupled device (CCD) or the like, that digitizes a stream of image data from the document 60 for transmission as representative electrical signals to a user device (not shown) such as a computer. After being scanned, the document 60 exits the image capture apparatus 30 via the document exit section 43.
Generally the documents 60 that are scanned by the prior art image capture apparatus 30 are of various thicknesses, ranging usually from about 0.04 mm to 0.4 mm. It follows that the aperture plates 56 have to be set far enough apart to allow the passage of the thickest documents 60. Still further, the documents 60 have to be properly supported as they pass through the space between the aperture plates 56, otherwise the positional condition of a document 60 and its image deteriorates. Therefore, the thinner the document 60 is, the more pronounced this deterioration becomes.
More specifically, with respect to the length of documents 60 relative to the direction of travel (shown by the arrow 62 in the exit section 43), for a long document 60, the leading edge of the document 60 conveyed into the aperture plates 56 is unsupported until the leading edge is between the guide rollers 59 that guide each document to the exit section 43. On the other hand, a document 60 that is shorter than a length of the aperture plates 56 is pitched unsupported through the aperture plates 56. Thus, when a document 60 that is to be scanned is thin so that there is a gap between the aperture plates 56 and the document 60, the scanning procedure gives rise to problems such as a wrinkling of the document 60, and a side-to-side movement of the document 60. This causes a distortion and blurring of text characters, drawings, and other such information included on the document 60 being scanned.
It is desirable to provide an image capture apparatus which scans documents of various thicknesses and lengths through a pair of mutually opposing aperture plates without the documents either oscillating from side-to-side or becoming wrinkled to thereby avoid distortion or blurring of the resulting images of the documents being scanned.